Neck fold measurement is a non-invasive examination performed at 12 to 14 weeks of pregnancy. A high-resolution ultrasound machine is used to determine the thickness of the neck fold of the unborn baby. This allows conclusions to be drawn about any genetic disorders.
What is nuchal fold measurement?
A high-resolution ultrasound machine is used to determine the thickness of the neck fold of the unborn baby. From this, conclusions can be drawn about any genetic conditions. Between the 11th and 14th week, the baby develops an accumulation of water in the neck area. If this area is enlarged, this may indicate genetic defects (e.g. Down syndrome) or heart defects. Nuchal fold measurement is also called nuchal density measurement, nuchal translucency measurement or NT screening. It is not a diagnostic method that could provide information about an actual disease. Rather, it is a statistical estimate of the likelihood of the baby having a malformation. It takes into account not only the nuchal fold width, but also the size and age of the embryo and the age of the mother. An increased value for the nuchal fold width does not mean that the baby will be born handicapped. It only means that the probability of a malformation in the child is increased. Only further examinations can provide certainty. Also, an inconspicuous value of the nuchal fold width is not a guarantee of a healthy child.
Function, effect, and goals
During pregnancy, the lymphatic system and kidneys develop in the unborn baby. Until they are fully formed, the body cannot eliminate accumulating fluid. It accumulates in the neck between the skin and soft tissues. This neck fold is not dangerous for the child and disappears in the course of development. Neck fold measurement can only be performed at two to three weeks of pregnancy. The time window for this examination is so small because the baby is still too small before the 11th week of pregnancy. This would make the measurement too inaccurate. From the 14th week of pregnancy, the baby’s kidneys are developed and the accumulation of water in the neck is resolved by them. Therefore, the optimal time for the examination is the 12th week of pregnancy. Due to its fluid filling, the nuchal fold appears transparent in the ultrasound. For the examination, the gynecologist must have special training and have a high-resolution ultrasound machine. Usually, the ultrasound examination is performed through the mother’s construction blanket. Only if the baby is lying awkwardly, a vaginal examination is performed. Great care is required during the procedure. For example, the measurement must not be taken too deep in the baby’s neck, otherwise the width value will be incorrectly obtained. The aim of neck fold measurement is not to determine the health of the child. This examination cannot do that. It only provides a statistical statement about the probability that the child will be born without disability. Values of 1 to 2.5 millimeters for the nuchal fold are considered normal. Values of 3 millimeters or more are considered increased, and values of 6 millimeters or more are considered very high. Assuming correct measurement, the probability of malformation in the baby increases with increasing value of nuchal fold width. The possible malformations are trisomy 21 (Down syndrome), trisomy 13 (Pätau syndrome), trisomy 18 (Edwards syndrome) or heart defects. Both trisomy 13 and trisomy 18 result in severe organ malformations and a very short life expectancy, usually not extending beyond infancy. Measuring the width of the nuchal fold does not provide information about which maldevelopment may be present. Further examinations are required for this purpose. This examination is recommended for mothers over 35 years of age, if abnormalities have been detected in previous ultrasound examinations, in high-risk pregnancies and if there is an increased risk of genetic defects in the family. Neck fold measurement is not a standard service provided by health insurance companies. Therefore, it is only paid for by the insurance companies in exceptional cases. Affected women should, however, feel free to ask. If the examination must be paid for by the patient, the costs range from €30 to €200.
Risks, side effects and dangers
Since the neck fold measurement is an ultrasound examination, it is completely risk-free for mother and child.Difficult are the psychological problems and the relative uncertainty of the examination. It very often gives false positive results. In 5% of examinations, an increased value for the nuchal fold width is found. Then additional examinations are necessary. Nut in 10 % of the cases these examinations then really show a disability of the baby. On the other hand, even with a normal value for the nuchal fold width, a disability cannot really be ruled out. Only an amniocentesis can provide final clarity. However, this is associated with the risk of miscarriage. Mothers should therefore only have a nuchal fold measurement if there is a real reason for it. Otherwise, they may worry unnecessarily and possibly take unnecessary risks. They should also discuss with their partner what should happen in case of an elevated value. Do they want to take the risk of an amniocentesis to have clarity? How do they react if a disability is really detected? If in doubt, are they prepared to have an abortion? Further, it should be noted that approximately 20% of all children born with Down syndrome have not shown an enlarged nuchal fold. Thus, the nuchal fold measurement can only ever be seen as an indicator of a possible disability. It creates a suspicion, not clarity. This can only be obtained by supplementary investigations.
